Rapid cool process

ABSTRACT

Rapid cooling of molded workpieces formed in an injection molding machine such as PET parisons is provided by a receiver receiving molded workpieces upon ejection from the molding machine, the receiver being transported out of the molding machine to an adjacent position where a cooling head coupled to a source of cooling fluid such as liquid CO 2  directs the fluid toward the surfaces of each workpiece. The cooling head engages and is sealed to the receiver to inhibit the escape of cooling fluid into the atmosphere thereby reducing cost, environmental impact, etc. A sensor coupled to a control of the cooling fluid source permits the release of cooling fluid from said source to contact the workpieces only when the cooling head is engaged with and sealed to the receiver. A vacuum unit withdraws cooling fluid from the receiver subsequent to contact between the workpieces and the cooling fluid. The cooling fluid is then recooled and recycled for reuse.

CROSS-REFERENCE TO RELATED APPLICATION

This document is a divisional application of parent U.S. patentapplication Ser. No. 07/646,071 filed Jan. 25, 1991, entitled RAPID COOLAPPARATUS now U.S. Pat. No. 5,114,327.

BACKGROUND OF THE INVENTION

This invention relates generally to apparatus for use in conjunctionwith injection molding machines for rapidly cooling work pieces moldedby the molding machine. The invention relates particularly to a methodand apparatus for rapidly cooling injection molding parisons to beemployed in the manufacture of biaxially oriented articles such ascontainers for carbonated beverages and the like.

The manufacture of biaxially oriented containers such as those formedpolyethylene terephthalate (PET), employs an initial step of forming aparison or preform by an injection molding process. The parisons aregenerally in the shape of a hollow cylinder closed at one end and areoften formed in multicavity molds into which plastic material isinjected around a core positioned within each cavity. Generally the coreand cavity are cooled by means of a liquid flowing through channelswithin the walls of the core and cavity thereby cooling the plasticforming the parison to a form-stable shape defined by the core andcavity.

Once the parison is formed and cooling is initiated, the core andparison are removed from the cavity thereby exposing the outer surfaceof the parison to room temperature air. An ejector or stripper mechanismthen strips the parisons from the cores to expose the inside surface ofthe parisons to room temperature air and to free the molding machine toinitiate another molding cycle. As the parisons are stripped from thecores, any contribution by the cores to the form stability of theparisons is also removed thereby freeing the parisons to be modifiedfrom their initially molded shape by outside forces.

In order to reduce this post molding modification of parison shape, itis desirable that the preform be cooled as much as possible therebyenhancing its form stability. The cooling can be enhanced by merelyretaining the molded article in contact with the cooled cavity and corefor an extended period of time thereby allowing additional heat to beextracted from the parison. This has the undesirable affect of extendingthe time for each injection molding cycle thereby reducing the number ofparisons which can be produced in a given unit of time.

In order to enhance the cooling of the parisons, it has been suggestedto provide additional cooling apparatus. In one such apparatus disclosedin U.S. Pat. No. 4,472,131, the parison, while retained on the core rodof the mold, is positioned within a supercooling mold. The outer surfaceof the parison cools either by direct contact with the wall of thesupercooling mold or by cold air passing through an air gap between theouter surface of the parison and the supercooling mold. The coldcompressed air is introduced at a point corresponding to the tip orsprue end of the preform. After passing along the length of the outerwall of the preform, the air escapes through holes located in the moldadjacent to the preform neck ring or thread finish During the cooling,the parison is retained on the core rod of the initial mold in which theparison was formed. Thus in order that the molding cycle of the moldingmachine may continue, duplicate core rods and shifting mechanisms forthose core rods must be supplied to permit a reasonable production ofparisons in a given unit of time.

In another disclosure of cooling apparatus found in U.S. Pat. No.4,592,719, the parison is removed from the core rod on which it wasformed by a pneumatic grip which draws atmospheric air by suction alongthe length of the parison between the parison outer wall and thepneumatic grip. The grip then removes the parison from the moldingmachine where a second grip is introduced into the interior of theparison. The second grip also causes atmospheric air to be sucked alongthe inner walls of the parison thereby enhancing the cooling of theparison through turbulent contact with a large volume of ambient air.

While such apparatus speeds the cooling of the parisons to an acceptableform stable temperature in a shorter time than would be experienced bymere contact with ambient air in the absence of such apparatus, furtherreductions in cooling time are desirable which would allow evenadditional increases in parison production from a given molding machine.Thus an object of the present invention is to develop a method andapparatus for reducing the time period of the cooling of the preformsubsequent to injection molding thereby enhancing the productivity ofthe associated injection molding machine.

SUMMARY OF THE INVENTION

In accordance with the present invention, an apparatus is provided foruse with an injection molding machine which includes a receiver meansfor receiving molded work pieces upon ejection of the work pieces fromthe molding machine A transporter means is coupled to the receiver meansfor transporting the receiver means relative to the molding machine froma first position within the injection molding machine to a secondposition adjacent to the injection molding machine A source of coolingfluid is provided together with a directing means for directing thecooling fluid toward the surfaces of each work piece in the receivermeans. A moving means coupled to the directing means moves the directingmeans relative to the receiver means from a disengaged position to anengaged position where the directing means and receiver means areengaged with each other. Sealing means is provided for sealing thedirecting means to the receiver means to restrict any escape of coolingfluid while the directing means and receiver means are engaged with eachother. Control means coupled to the source of cooling fluid andresponsive to the relative position of the receiver means and directingmeans releases cooling fluid from the source only when the directingmeans and receiving means are engaged and are sealed by the sealingmeans. A vacuum means is coupled to the receiver means for withdrawingcooling fluid from the receiver means subsequent to contact between thework pieces and the cooling fluid.

One feature of the present invention is the application of a continuousflow of cooling flow to both the internal and the external surfaces of awork piece while it is completely enclosed. This feature provides theadvantage of confining the cooling fluid so as to contact the work piecerepeatedly thereby insuring the extraction of a maximum amount of heatfrom the work piece with the minimum amount of cooled fluid to achieve ahigh efficiency heat extraction.

An important feature of the present invention is the employment of aseal means between the receiver means and the directing means whichprevents the escape of cooling fluid during the cooling process therebypermitting a recycling of the cooling fluid through a vacuum system.This feature has the advantage of permitting the use of fluids which dueto cost, environmental impact, or other factors, might otherwise not befeasible. The preferred cooling fluid to be employed in the presentinvention is that of liquified carbonic (liquid CO₂).

While the invention is hereafter described in connection with theparticular application of the methods and apparatus herein disclosed tothe molding of PET parisons for subsequent manufacture into biaxiallyoriented containers for carbonated beverages and the like, it will beappreciated that the rapid cooling system in accordance with the presentinvention could be employed for work pieces of a character other thanparisons. Additional features and advantages of the invention willbecome apparent to those skilled in the art upon consideration of thefollowing detailed description of a preferred embodiment exemplifyingthe best mode of carrying out the invention as presently perceived. Thedetailed description particularly refers to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an apparatus in accordance with thepresent invention.

FIG. 2 is a sectional detail view of a receiving means in accordancewith the present invention.

FIG. 3 is a sectional detail view of a directing means in accordancewith the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An apparatus 10 for use with an injection molding machine 12 is shown inFIG. 1. The injection molding machine 12 is illustrated only in part toprovide an illustrative environment for the apparatus 10. The injectionmolding machine 12 includes an injection unit 14 which acts to supplyplastic in a molten form to a plurality of cavities 16 in cavity unit18. Each cavity 16 in the cavity unit 18 has a corresponding core 20fixed to core unit 22 which moves relative to the cavity unit 18 bymeans of a power actuated toggle system 24 or similar apparatus as isconventional in the industry. The core unit reciprocates in thedirection "A" so that the cavity 16 and cores 20 cooperate to define anessentially closed chamber in which a work piece such as a parison canbe formed. Subsequent to the formation of the parison between core andcavity, the cavity unit moves to the position illustrated in FIG. 1 andthe molded parisons are stripped from the cores 20 by a stripper plate26 as is conventional in the industry.

The apparatus 10 in accordance with the present invention includes areceiver means in the form of a receiver frame 30. The receiver frame 30includes a plurality of chamber elements 32 in a pattern which willpermit the chamber elements to receive the molded parisons as they arestripped from the cores 20 of the injection molding machine 12 bystripper mechanism 26. The receiver frame 30 is suspended from anoverhead track 34 serving to define a pathway along which the receivertravels in the direction "B". A transport mechanism of conventionaldesign including vertical hanger 36 transports the receiver frame 30from a first position within the injection molding machine 12 so thatthe chamber elements 32 are aligned with the cores 20 to a secondposition adjacent to the injection molding machine 12 as shown in FIG.1.

The receiver frame 30 is coupled to the vertical hanger 36 by adischarge unit 38 which is adapted to pivot the receiver frame 30 abouta horizontal axis in the direction of arc "C" so as to unload thecontents of the chamber elements 32 onto conveyer belt 40 or othersimilar conveying means for conveying the parisons from the position ofthe molding machine 12 to a subsequent processing operation. Once theparisons have been removed from the molding machine and prior to theirbeing discharged by discharge unit 38, they are subjected to a coolingfluid such as liquid carbonic taken from source 42.

The source of cooling fluid 42 is connected by flexible conduit 44 to acooling head 46. The cooling head 46 is suspended from track 48 which isperpendicular to track 34 and defines a pathway for movement of thecooling head 46 with respect to the receiver frame 30 when the receiverframe is in the position illustrated in FIG. 1. A moving means ofconventional design including vertical support 50 causes the coolinghead to move in the direction "D" between a disengaged position as shownin FIG. 1 and an engaged position where the cooling head 46 and receiverframe 30 are engaged with each other. A sealing means, not illustratedin FIG. 1, seals the cooling head to the receiver frame so as to inhibitany escape of cooling fluid while the cooling head and receiver frameare engaged with each other.

A control means 52 which can be in the form of a microswitch or othersimilar sensor is coupled to the source of cooling fluid 44 by anappropriate cable 54. The control unit 52 is responsive to the relativeposition of the cooling head 46 and receiver frame 30 so as to causerelease of cooling fluid from source 42 only when the cooling head 46 issealed to the receiver frame.

A vacuum unit 56 is coupled to the receiver frame 30 by means of anappropriate flexible conduit 58 for withdrawing the cooling fluid fromthe receiver frame 30 subsequent to contact between the cooling fluidand the parisons held within the chamber elements 32. A recycling unit60 which can include a fluid chiller and pump of conventional designrecools the cooling fluid received by the vacuum unit 56 and recyclesthe cooled and filtered fluid to the source 42 for subsequent use.

As shown in FIG. 2, the receiver frame 30 is defined by a plurality ofperimeter plates 62 which cooperate to define the overall geometry ofthe receiver unit 30. A vacuum plenum 64 is provided at the rear of thereceiver unit and is coupled to the flexible conduit 58 discussedpreviously. The chamber elements 32 are each coupled by a threadedelement 66 to the vacuum plenum. Each of the chamber elements is seen toconstitute a generally cylindrical wall member 68 extending forward fromthe threaded element 66 through an opening in front wall 70.

Each chamber element 32 includes an inwardly directed lip 72 at themouth of the cylindrical wall 68 adapted to engage the lower surface ofa radially extending flange 74 on parison 76 so as to suspend theparison within the chamber element 32 such that a small space isprovided between the outer wall 78 of parison 76 and the inner surface80 of wall member 68 A plurality of openings 82 on the front face 86 ofthe chamber elements 32 provide a pathway for cooling fluid to enter thespace between the parison outer wall 78 and the chamber element innerwall 80. A sealing groove 84 surrounds the plurality of openings 82 onthe front face 86 of the chamber elements 32.

A cooling head 46, shown in greater detail in FIG. 3, is coupled toconduit 44 which supplies cooling fluid from source 42 shown in FIG. 1to a pressure plenum 88. The cooling head 46 includes a plurality ofstem elements 90 which are adapted to project into the interior of theparison 76 and include a plurality of small apertures 92 through whichcooling fluid passes to cool the interior surface of the parison. Thecooling fluid passes from the pressure plenum 88 into the stem elements90 through hollow threaded element 94 which element also secures the twopiece cap unit 96 to the forward plate 98 of the pressure plenum 88. Thetwo element cap unit 96 comprises a base member 100 and a finishenclosing member 102 which are sealed or bonded together to form asingle unit. A plurality of apertures 104 lead from a top chamber 106into the finish receiving chamber 108. The lip 110 of the finishenclosing member 102 includes a sealing means such as O-ring 112 to sealthe finishing closing member to the front face of the correspondingchamber element 32.

In use, a set of molded parisons 76 or other similar work pieces formedin an injection molding machine 10 are received by a receiver 30 uponbeing stripped from cores 20 by a stripper mechanism 26 The receiver 30is transported from a position within the molding machine 20 to a secondposition adjacent to the molding machine by a transporter mechanismfollowing a pathway 34. A cooling head 46 moves along a path 48perpendicular to pathway 34 to engage and be sealed to the receiverframe 30 such that stem elements 90 project down into the interior ofthe parison 76 which are retained within the hollow cylindrical walls 68of the chamber elements 32. Sensor 52 then activates the release of acooling fluid such as liquid carbonic from source 42 through conduit 44into pressure plenum 88.

The fluid then is distributed through openings 92 in stem 90 and 104 infinishing closing member 102 to the interior and top of the parison 76.The cooling fluid, prevented from escaping into the atmosphere by sealmeans 112, travels through openings 82 through the space between theouter wall 78 of the parison 76 and the inner wall 80 of the chamberelements 32 to further cool the exterior of the parison 76. Subsequentto contact with the walls of the parison 76, the cooling fluid is drawninto vacuum plenum 64 through hollow threaded member 62 by vacuum unit62. The cooling fluid is then recycled through the filtering unit 59 andchilling unit 60 back to the source of cooling fluid 42.

Following the cooling of the parisons, the cooling head 46 retracts tothe position shown in FIG. 1 and the receiver means is pivoted bydischarge unit 38 in the direction of arrow "C" to discharge the cooledparisons onto moving conveyer belt 40 or other similar product handlingdevice. During the cooling process, the injection molding machine 10 hasexecuted another molding cycle. Upon return of the receiver frame to thevertical position shown in FIG. 1, receiver frame is carried into thespace between the cavity unit 18 and stripper frame 26 to receiveanother set of parisons.

Although the invention has been described in detail with reference tothe illustrated preferred embodiment, variations and modifications existwithin the scope and spirit of the invention as described and is definedin the following claims.

What is claimed is:
 1. A method of rapidly cooling a set of moldedworkpieces formed in an injection molding machine, the method comprisingthe steps of:receiving said molded workpieces upon ejection from saidmolding machine on a receiver means; transporting the receiver meansrelative to said molding machine between a first position within saidinjection molding machine and a second position adjacent to saidinjection molding machine; providing a source of cooling fluid anddirecting means for directing the cooling fluid toward a surface of eachworkpiece in the receiver means; moving the directing means relative tothe receiver means between an engaged position where the directing meansand receiver means are engaged with each other and a disengaged positionwhere the directing means and receiver means are spaced from each otherby a minimum distance; permitting the release of cooling fluid from saidsource to contact the workpieces only when the directing means isengaged with the receiver means at the engaged position; sealing thedirecting means to the receiver means when the directing means is at theengaged position to inhibit the escape of cooling fluid into theatmosphere; and withdrawing cooling fluid from the receiver meanssubsequent to contact between the workpieces and the cooling fluid. 2.The method of claim 1 further comprising the step of recycling thewithdrawn cooling fluid through a cooler to permit reuse of the coolingfluid.
 3. The method of claim 1 wherein the receiving step furthercomprises the step of positioning an outside surface of said workpiecesin spaced-apart relation from the receiver means to allow cooling fluidto contact said outside surface of the workpieces.
 4. The method ofclaim 1 wherein the permitting step further comprises the steps ofsensing the relative position of the receiver means and the directingmeans, and allowing a flow of the cooling fluid through the directingmeans toward said workpieces only when the receiver means and thedirecting means are contiguous to each other.
 5. The method of claim 1further comprising the step of discharging the workpieces from thereceiver means subsequent to cooling of the workpieces by the coolingfluid.
 6. The method of claim 5 wherein the discharging step furthercomprises the step of rotating the receiver means through an anglesufficient to cause said workpieces to be dumped from the receivermeans.
 7. A method of rapidly cooling a set of molded workpieces formedin and ejected from an injection molding machine, the method comprisingthe steps of:receiving the set of ejected workpieces from the moldingmachine in a receiver frame; transporting said receiver frame, relativeto the molding machine, from a first position within the molding machineto a second position adjacent to the molding machine; engaging a coolingdirector with said receiver frame; introducing cooling fluid from saidcooling director on each workpiece in said receiver frame; andwithdrawing the cooling fluid after contact with each workpiece in saidreceiver frame to permit recycling the withdrawn cooling fluid byrepetition of said stop of introducing cooling fluid using saidwithdrawn cooling fluid.
 8. The method of claim 7 wherein the workpieceshave an interior space and an outside surface and wherein the receivingstep further comprises the step of positioning an outside surface ofsaid workpieces in a spaced-apart relation from said receiver frame toallow cooling fluid to contact the workpieces.
 9. The method of claim 8wherein the introducing step includes the step of allowing cooling fluidto flow into the interior space and then around the outside surface ofeach of the workpieces in said receiver frame.
 10. The method of claim 7further comprising the step of discharging the workpieces from saidreceiver frame subsequent to the cooling of the workpieces by thecooling fluid.
 11. The method of claim 10 wherein the discharging stepfurther comprises the step of rotating said receiver frame through anangle sufficient to cause said workpieces to be dumped from the receivermeans.
 12. A method of rapidly cooling a set of molded workpieces formedin and ejected from an injection molding machine, the method comprisingthe steps of:receiving the set of ejected workpieces from the moldingmachine in a receiver frame; transporting said receiver frame, relativeto the molding machine, from a first position within the molding machineto a second position adjacent to the molding machine; engaging a coolingdirector with said receiver frame; introducing cooling fluid from saidcooling director on each workpiece in said receiver frame; withdrawingthe cooling fluid after contact with each workpiece in said receiverframe; and sensing the relative position of said receiver frame and saidcooling director, and allowing a flow of the cooling fluid through saidcooling director toward the workpieces only when said receiver frame andsaid cooling director are contiguous to each other.
 13. The method ofclaim 12 wherein the step of allowing a flow of the cooling fluidthrough said cooling director toward the workpieces is accomplished in asealed and fluid-tight manner such that no cooling fluid can escape intothe surrounding environment.